What is Silicon manganese?

Silicon manganese is a chemical compound made by mixing natural silicon with manganese, an element found naturally in the earth. When combined, these elements can be used to produce a number of specialty steel alloys. Silico manganese enhances the natural properties of steel, giving it increased strength and function, as well as improved aesthetic appeal. This means that silicon manganese alloys can be used in applications beyond those associated with standard steel products. Silicon manganese may also be known as ferro silico manganese or abbreviated as SiMn.

Silicon Manganese may be used alone, or combined with other substances to create various alloys. The ratio of silicon to manganese can also be adjusted to give steel the desired properties. Standard silicon manganese steel alloys contain 14 to 16 percent silicon, and as much as 68 percent manganese. They also include small amounts of carbon, which is required for the steel to undergo a chemical reactions with these compounds. In stainless or specialty steel products, the silicon content can be as high as 30 percent.

Silicon manganese alloy is an alloy composed of manganese, silicon, iron and a small amount of carbon and other elements, is a widely used, large production of iron alloy. Guimeng alloys is a complex deoxidizer for steelmaking commonly used, and is producing medium and low carbon ferromanganese smelting agent and electro silicothermic process production of manganese metal. Guimeng alloys can take continuous smelting operation in large, medium and small ore heat furnace. In steel production only by manganese or silicon deoxidation, loss rates were 46% and 37%, and the use of silicon manganese alloy burning loss rate is 29%.

Therefore, the production of iron and steel in order to reduce the production cost, in recent years by silicon manganese alloy instead of pure silicon, manganese, silicon manganese alloy, so in recent years the growth rate higher than that of steel production speed, usually silicon manganese alloy steelmaking using known as commodity Si Mn alloy, the use of low carbon Si Mn alloy smelting silicomanganese alloy called for their own use, the use of manganese metal called silicon manganese alloy, carbon in silicon manganese alloy below 1.9% or used for semi-finished products of producing medium and low carbon ferromanganese and electrical silicon hot metal manganese. And silicon manganese alloy demand at the rate of 15% per year increase, in the iron and steel industry production gradually take the place of ferrosilicon, widely used.

The production of silicon manganese alloy raw materials are manganese, manganese rich slag, silica, dolomite (or coke, limestone, fluorite). Production of manganese silicon alloy can use a manganese or manganese (including several manganese rich slag) mixed ore. Because the silicon manganese alloy iron and phosphorus requirements than high carbon ferromanganese is low, so the requirement of smelting manganese silicon manganese ore is higher than phosphorus and manganese than ferromanganese. The use of manganese ore containing manganese is higher, the better the indicators.

The main raw material of silicon manganese alloy production unit of the project of a manganese (340000t/a), manganese rich slag (112000t/a), intends to import high grade manganese ore from Gabon, Brazil, Garner, South Africa, rich manganese slag is supplied by the five southwestern provinces Guizhou, Sichuan, Guangxi, Yunnan, Hunan area, the main raw material silica source security. Auxiliary materials such as silica, coke supply by region and Inner Mongolia surrounding areas.

 

What is Silicon manganese used for?

Manganese and silicon are crucial constituents in steelmaking, as deoxidants, desulphurizers and alloying elements. Silicon is the primary deoxidizer. Manganese is a milder deoxidizer than silicon but enhances the effectiveness due to the formation of stable manganese silicates and aluminates. It also serves as desulphurizer.
Manganese is used as an alloying element in almost all types of steel. Of particular interest is its modifying effect on the iron-carbon system by increasing the hardenability of the steel. About 93 % of all manganese produced is in the form of manganese ferroalloys. The FeMn grades are high-carbon (HC), medium carbon (MC), low-carbon (LC) and very low carbon (VLC), whereas the SiMn grades are medium carbon (MC) and low carbon (LC). The steel industry is the only consumer of these alloys.
However as the average consumption of Mn in one tonne of steel is about 7 kg, this amounts to considerable tonnages. To cover the need for manganese and silicon, the steelmaker has the choice of HCFeMn, SiMn and FeSi in a blend governed by specifications on carbon, silicon and manganese. Commonly a mixture of HCFeMn and FeSi75 is used, but a trend towards more use of SiMn is seen at the expense of the two others. This is primarily for economic reasons.

The economics of silicomanganese smelting is enhanced by minimising the loss of manganese as metal inclusions, as MnO dissolved in the slag, and by production of metal high in silicon and low in carbon. The SiMn production is typically integrated with the manufacture of HCFeMn so that the slag from the HCFeMn production is reprocessed in the production of SiMn. In this way a very high total yield of manganese is achieved.

Production process

The economics of silicomanganese smelting is enhanced by minimising the loss of manganese as metal inclusions, as MnO dissolved in the slag, and by production of metal high in silicon and low in carbon. The SiMn production is typically integrated with the manufacture of HCFeMn so that the slag from the HCFeMn production is reprocessed in the production of SiMn. In this way a very high total yield of manganese is achieved.
Production process

Production process of Silicon manganese

Silicomanganese is produced by carbothermic reduction of oxidic raw materials in electric submerged arc furnaces. The same type of furnaces is used for FeMn and SiMn alloys. Operation of the SiMn process is often more difficult than the FeMn process because higher process temperature is needed. The size of the SiMn furnaces is usually in the range 15-40 MVA, giving 80-220 tonne of alloy per day. Standard silicomanganese with 18-20 % Si and about 70% Mn is produced from a blend of
HCFeMn slag with about 35 to 45% MnO, manganese ores, quartzite, (Fe)Si-remelts or off grade qualities, and coke. Sometimes minor amounts of MgO-containing minerals are added, e.g. dolomite [CaCO3⋅MgCO3] or olivine [(MgO)2⋅SiO2].

The discard slag from the SiMn process normally contains 5 to 10% MnO. Low carbon silicomanganese with around 30% Si is produced by upgrading standard alloy by addition of silicon wastes from the ferrosilicon industry. Manganese ores normally contain unwanted elements that can not be removed in the mining and processing stages. Of special importance is phosphorus due to the strict demands in respect of this element both in the FeMn and SiMn alloys. Iron, phosphorus and arsenic are
reduced more easily than manganese and will consequently go first into the metal. Their content in the final alloy must therefore be controlled by selection of ores. The HCFeMn slag is a very pure source of manganese because the easily reduced impurities in the ores have been taken up by the HCFeMn metal in the preceding process step.

 

The content of impurities, like phosphorus, in SiMn alloys is therefore controlled, not only by the selection of manganese ores, but also by the relative amounts of manganese ores and HCFeMn slag in the raw material mix. A process temperature of 1600 to 1650°C is necessary to obtain metal with sufficiently high content of Si and discard slag with low MnO. FeMn slag has a relatively low melting temperature (about 1250°C) compared with Mn-ores. Accordingly, a high share of FeMn slag will tend to give lower process temperatures[1]. When the Mn-ore starts melting at around 1350°C[2], it will contain a mixture of a solid and a liquid phase, where the solid phase is MnO. Further heating and reduction to 1550°C or more is necessary before the melting ore will mix with the slag and flow freely.

With a high share of Mn-ore in the mix, the surface temperature and process temperature in the cokebed zone will be higher. The specific power consumption for production of standard SiMn from a mixture of Mn-ore, HCFeMn slag and Si-rich metallic remelts, can typically be 3500-4500 kWh/tonne metal, dependent first of all on the amount of metallics added to the feed. The power consumption will increase
with the Si-content of the metal produced, and also with the amount of slag per tonne of SiMn. Each additional 100 kg slag produced will consume additionally about 50 kWh electric energy. About 100 kWh per tonne of metal and some coke will be saved if the ore fraction in the charge is reduced to MnO by CO gas ascending from the smelt reduction zone.
The production process of silico manganese goes through stages such as smelting, and slag formationandreduction. Here is the detailed discussion on the stages:

Stage 1:
It revolves round heating and pre reduction in the solid state at 1373 K and 1473 K. The manganese oxide content is reduced to manganese monoxide and iron oxides to metallic iron.
Stage 2:
In this stage formation of liquid slag and manganese oxide reduction takes place. Slag samples are taken from the top of the coke bed at 1773 K with ferromanganese in a furnace.

Since, liquid slaghave a low viscosity to percolate through the coke bed, the top of the coke bed is normally kept at 1823 K to 1873 K.
Stage 3:
Reduction reactions change the ore composition which in turn changes the melting temperature and other properties of ore. At low temperatures the gas contains carbon dioxide and water near the top of the furnace.

The slag obtained is mostly used as an active source of manganese in the production of silico manganese. Plus, the use of ferro manganese slag in silico manganese production leads to the increase of energy consumption by 500 kWh/t slag.

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